The present invention relates to a dental anchor or pin for aiding in the retention of a dental restoration and, more particularly to a dental anchor provided with means for reducing stress both upon a tooth stub in which it is inserted as well as reducing cracks in the restoration which is built up over the anchor.
Dental anchors or pins for retaining dental restorations are well-known in the art of dentistry, particularly anchors or pins having threads thereon for securement in the tooth structure. The tooth stub is typically prepared by cutting it down and making a bore in the tooth stub, in which a dental post is inserted. Additional bores are formed in the tooth structure, into which pins or anchors are threaded. These pins have portions extended upwardly of the tooth surface for aiding in the retention of the dental restoration as well as avoiding rotation of the restoration on the tooth stub. Such anchoring pins are very small, i.e. in order of 0.03 inches in diameter and 0.2 inches in length. These pins are typically first loaded into a dental power tool or holder and inserted into prepared bores or channels made in the body of the tooth. Such bores or channels are formed in the body of the tooth by means of dental drills.
Anchors or pins for anchoring and supporting a dental restoration are typically comprised of two portions, one of which is an anchoring portion threaded in the bore formed in the body of the tooth and another is a retention portion for embedding into the restoration. Typically the retention portion is coupled to a manipulating head extending from the retention portion and connected by at least one reduced diameter portion. In this way when the pin is threaded into the bore formed in the tooth the pin severs automatically upon bottoming out the lower end of the bore. The anchoring portion remains in the tooth with the retention portion extending upwardly from the tooth surface.
Dental anchors or pins having a buttress-type thread has been disclosed in assignee's co-pending patent application Ser. No. 191,347. They have proven to have a most satisfactory retention capability inasmuch as buttress-type threads, particularly the reverse buttress-type threads described, provide improved holding power in the dentition and reduce the amount of dental damage during insertion.
The aforementioned co-pending application discloses a dental anchor having a buttress-type thread, where the buttress-type thread includes a substantially planar lower surface facing toward the insertion end of the dental anchor, a beveled upper surface which tapers inwardly towards the retention portion of the dental anchor, and a sharp crest portion disposed between the planar lower surface and angled upper surface. A top member or collar is provided between the anchoring portion and the retention portion. The stop member limits the depth of insertion of the dental anchor into the bore.
It should be appreciated, however, that even with highly efficient dental anchors or pins having buttress-type threads there is a continuous interest in further reducing or minimizing any stress on existing dentin, especially at the bottom or seat portion of the bore which receives the dental anchor.
Accordingly, while the use of dental anchors having a buttress-type threads thereon has been proven quite useful in the dental art, further improvements in such dental anchors and means for anchoring the same in the tooth body are still of importance in order to yet further reduce any stress on dentin material and to facilitate anchoring or such pins. It is also of interest to facilitate insertion at surfaces of teeth which are inclined, curved or have any other non-planar exposed surfaces.